Wildfires Cause Cooling in Arctic

Wildfires in Alaska and Canada Had Net Cooling EffectProving that climate science can be anything but intuitive, researchers report that large wildfires could have a net cooling effect. Led by Robert Stone, at the University of Colorado in Boulder, the team studied the wildfires that ravaged Alaskan and Canadian wilderness in 2004. The work is credited with creating a better understanding of the impact of particles and smoke in the atmosphere, which has been one factor of uncertainty in climate models. California Wildfires Won't Impact AlaskaResearchers point out that smoke from the California wildfires are unlikely to affect the arctic, because air circulation patterns do not favor the smoke reaching the arctic. However, wildfires in Siberia could affect the Arctic in addition to fires such as those in 2004 which burned in Western Canada and Alaska.

Reflected Radiation and Absorbed WarmthThe researchers measured the smoke density and the amount of energy from sunlight reaching the ground level through the wildfire smoke, to see the relationship between the amount of smoke and the reduction of net energy reaching the ground. The team found that although particles in the atmosphere absorb energy above the ground, they also reflect incoming radiation and prevent this from warming the ground below the cloud of smoke. The net effect of both influences is cooling, which is more notable when the smoke is over dark surfaces which would otherwise efficiently absorb the incoming radiation.

Uncertainties RemainAdditional uncertainties remain which are not addressed by the University of Colorado Boulder study. For example, the study does not address the tendency of particles to affect cloud formation, either by evaporating clouds due to the warmth collected in the particle mass, or by "seeding" clouds by triggering condensation on the particles.

Since wildfires are a natural phenomena, where does mankind fit into the climate change-wildfire impact continuum? Climate change models predict more fires due to drought conditions in global warming scenarios; sustainable forestry reduces wildfire risks. Studies such as this help us to understand the delicate balance.